I'm at the end of a long but gratifying week shooting in Austin. The rest of the crew has gone home and I have one evening with the city all to myself. I'm scratching my time lapse itch and loving every minute of it. Not to mention taking the rare opportunity to connect with old friends. Loving life right now even though I miss being home.
Tonight I stitched the 5 rear angles of a potential plate rig configuration for the first time and susequently solved one of the nagging problems I've had with all of my driving plates to date.
When a car turns a corner, its front wheels follow an arc path, the rear wheels follow a shallower arc as they follow through the curve. Because a rear facing plate camera will always be mounted on the rear of the plate car, in some cases well behind the rear wheels, the camera is tracking the wrong arc as compared to the foreground camera that would have been mounted on the front of the car. The effect of this in the composite is that it looks like the car is spinning like a top, the background appears to slip by as the car completes a turn.
By having the flexibility of using panoramic plates, we can force the camera to follow the correct arc by animating a new path with keyframed back-panning. I instinctively do this when operating the Libra head on the camera car, slightily delay the pan to hold the vanishing point of the old street for as long as possible before back panning to catch the line of the new street. This same thing can be accomplished by keyframing the x-position of the stitched plate. Three keyframes are needed, first and last correspond to the frames where the plate car is entering and exiting the turn. The middle keyframe should be just slightly prior to the mid point of the first and last keyframe. This keyframe value should be set to hold the vanishing point of the old street for as long as practical.
I've just stumbled onto a blast from the past. Here is a clip from the Digital Cinema Training Course that I recorded a few years back. Watch as I take you step by step through the process and techniques for compositing and shooting for Green/Blue Screen. Enjoy, and mock as necessary!
I'm working on a complete journal of the experience I had visiting Joplin last week, in the mean time, here is a quick glimpse at what we saw...